Magnetic recording media using ferromagnetic metal particles which have high saturation magnetization (os) and high coercive force (Hc) have been studied and developed for the purpose of improving the recording density and improving the reproduction output.
Although the ferromagnetic metal particles have excellent magnetic characteristics, they are difficult to disperse because of their high saturation magnetization and large interaction between particles, and their dispersion stability is not so good. Further, they have a problem in chemical stability and are easily oxidized. Therefore, magnetic recording media using the metal particles can easily develop problems relating to stability with the passage of time. Particularly, when a process which comprises wetting a magnetic recording medium and thereafter drying it is repeated, precipitates are formed on the surface thereof which damages the uniformity and flatness of the surface. Consequently, not only does the output obtained from the magnetic recording medium vary or the drop-out increase, but neither normal recording or reproduction can be carried out.
Hitherto, surface treatment of ferromagnetic metal particles with trialkoxysilane compounds such as vinyltriethoxysilane, .gamma.-methacryloxypropyltrimethoxysilane, glycidyloxypropyltrimethoxysilane and methyltrimethoxysilane have been known, as described in Japanese Patent Publication No. 4803/80. However, the thus treated metal particles do not have sufficient dispersiblity, oxidation stability and corrosion resistance.